This disclosure concerns a solenoid valve assembly. More specifically, this disclosure describes a solenoid actuated brake or actuator assembly.
A wide variety of electrohydraulic pressure reducing and relieving valves are used to provide controlled pressure to hydraulic actuators and brake cylinders, for example. Some typical valves are designed for use with a proportional electric solenoid, which generates a thrust force proportional to the electrical current fed to the solenoid. The size and cost of the proportional solenoid are a function of the force output and the stroke over which this force output is available. Thrust force of proportional solenoid valves is proportional only within a predetermined stroke length. For a given size and cost, the predetermined proportional stroke length may be exceeded, but only with reduced force. Thus, to maximize the force capability of a proportional solenoid valve, it is desirable to maintain the stroke length within the proportional range. Typical proportional solenoid valves have moving armatures that travel farther than the proportional stroke range. Farther travel in the valve is desirable to provide for quicker activation or release of a working unit by increasing the flow rate through the valve body. Moving the armature as far over as possible in an activation or release position increases the flow rate. The problem is that as the stroke of the armature exceeds the proportional range, the thrust force rapidly decreases. Therefore, current designs are limited in providing adequate flow rate due to the constraint of the relationship between stroke length and force output.
In general, improvement has been sought with respect to such valve arrangements, generally to better accommodate increasing overall valve spool and armature travel while maintaining proportional stroke length to maximize force output.
One aspect of the present invention relates to a solenoid valve assembly having an auto-relieving valve arrangement that utilizes the maximum stroke length and force output of a proportional solenoid valve while providing added stroke travel to increase flow rate capacity without exceeding the solenoid""s proportional range.
Another aspect of the present invention relates to a valve arrangement having a biasing component that biases a spool in an energized direction, from a relieving position to a neutral position, without energizing a solenoid.